Fabrication of cobalt-nickel binary nanowires in a highly ordered alumina template via AC electrodeposition

Abstract

Cobalt-nickel (Co-Ni) binary alloy nanowires of different compositions were co-deposited in the nanopores of highly ordered anodic aluminum oxide (AAO) templates from a single sulfate bath using alternating current (AC) electrodeposition. AC electrodeposition was accomplished without modifying or removing the barrier layer. Field emission scanning electron microscope was used to study the morphology of templates and alloy nanowires. Energy-dispersive X-ray analysis confirmed the deposition of Co-Ni alloy nanowires in the AAO templates. Average diameter of the alloy nanowires was approximately 40 nm which is equal to the diameter of nanopore. X-ray diffraction analysis showed that the alloy nanowires consisted of both hexagonal close-packed and face-centered cubic phases. Magnetic measurements showed that the easy x-axis of magnetization is parallel to the nanowires with coercivity of approximately 706 Oe. AC electrodeposition is very simple, fast, and is useful for the homogenous deposition of various secondary nanostuctured materials into the nanopores of AAO.

Figure 1

Digital photos of AAO template without (a) and with (b) Co-Ni binary nanowire co-deposition.

Figure 2

FESEM image of AAO template. (a,b) Top surface view at low and high magnification. (c,d) Cross-sectional view at low and high magnification.

Figure 3

Schematic diagram for co-deposition process of Co-Ni binary nanowires in nanopores of AAO template. (a) AAO template with circular shape, (b) filling of nanopores started from Co-Ni binary nanowires at the bottom of AAO by exposing circular area to the Co and Ni precursor solution, (c) complete filling of the alumina nanopores from Co-Ni binary nanowires, (d) dissolution of alumina in NaOH to get Co-Ni binary nanowires.

Figure 4

SEM images of Co-Ni binary nanowires. (a) top surface and (b) cross-sectional view embedded in AAO template, (c, d) top surface view of Co-Ni binary nanowires partially liberated from AAO template at low and high magnification (e, f) tilted view at low and high magnifications.

Figure 5

EDX spectrum of Co-Ni binary nanowires [Co(II)/Ni(II) = 80:20]. Embedded in AAO template along with their quantitative analysis.

Figure 6

XRD pattern of the Co-Ni binary nanowires embedded in AAO template. Asterisks indicate fcc, while solid black circles indicate hcp Co-Ni binary nanowires.

Figure 7

Hysteresis loops of Co-Ni binary nanowire [Co(II)/Ni(II) = 80:20]. Measured at room temperature using vibrating sample magnetometer.